Prior computerized monitoring systems have utilized time synchronous averaging techniques to monitor the mechanical performance of machine equipment. A few applications have utilized on-line process sensors and time synchronous averaging techniques to correlate process variables occurring in the machine direction (MD) to equipment performance. However, such prior systems have not generally used multi-dimensional and time-synchronous mapping of production process variables to control or correlate to equipment or component performance.
In the field of on-line measurement of paper quality variables in paper production, conventional on-line techniques have used scanning sensors to take cross direction (CD) measurements of selected paper quality variables at intervals across the width of the moving paper web, however these do not provide information on variations occurring in the machine direction (MD). Prior paper quality monitoring techniques have not generally utilized real-time, on-line measurements of the running performance of paper machine elements, such as felt belts and rotating equipment, in order to assess their impact on paper quality.
Off-line measurements of paper quality variables generally take static or destructive tests of paper samples after a run. Such off-line measurements are difficult to correlate to real-time changes occurring in paper quality due to operational conditions in one or more machine components.
U.S. Pat. No. 5,358,606 to Makkonen proposes a system for recording on-line variations in paper characteristics along the run length (MD) of a paper web, recording the periodicities of motion or rotation of selected machine elements, and comparing any periodicity detected in an MD measurement with the periodicities of the machine elements in order to locate a possible fault in the operational condition of the machine elements. Sensors may be used to monitor web basis weight, thickness, smoothness, transmission, fiber orientation, permeability, water content, gloss, opacity, filler content, fluttering, etc. Synchronizing pick-ups are disposed on the machine elements to record their periodicities. A computer program detects when any periodicity in a measured variable correlates to the periodicity of a machine element, and reports a possible fault.
U.S. Pat. No. 5,400,258 to He discloses the use of an array of "bump" actuators across the width of a paper web and a CD profile analyzer to detect the resulting impacts in the CD zones and build an array of coefficients for accurately mapping the effects of an upstream variation with its downstream impact.
However, these proposed techniques only measure paper quality variables in one direction, i.e., either the MD or the CD, and do not show how the operational conditions of machine elements may have multi-dimensional or cross-correlated impacts over the entire paper web.